In general, Group III-V semiconductors made of compounds of Group III elements and Group V elements are widely used for devices such as light emitting diodes (LEDs).
A Group III nitride semiconductor using Al, Ga, In, or the like as a Group III element and using N as a Group V element has a high melting point and a high dissociation pressure of nitrogen, which makes it difficult to perform bulk single crystal growth. Further, conductive single crystal substrates having large diameter are not available at low cost. Accordingly, such a semiconductor is typically formed on a sapphire substrate.
However, since the sapphire substrate has an insulating property, electric current does not flow in the substrate. Accordingly, a lateral structure in which electric current flows in a lateral direction has been conventionally used. This structure is obtained by partially removing a light emitting structure laminate formed by sequentially growing an n-type Group III nitride semiconductor layer, an active layer (light emitting layer), and a p-type Group III nitride semiconductor layer on a sapphire substrate, to expose the n-type Group III nitride semiconductor layer, and providing an n-type electrode and a p-type electrode on the exposed n-type Group III nitride semiconductor layer and the p-type Group III nitride semiconductor layer, respectively.
In response to this, in recent years, the following technique for obtaining vertical structure LED chips has been studied. After forming a buffer layer made of a certain element other than a Group III element (for example, Al, Ga, or the like) on a sapphire substrate, a light emitting structure laminate is formed. The light emitting structure laminate is supported by a conductive support, and then a sapphire substrate is separated (lifted off) by selectively dissolving the buffer layer by chemical etching. The conductive support and the light emitting structure laminate are sandwiched between a pair of electrodes (see JP 4172657 B (PTL 1)). Note that a “buffer layer” herein is a buffer layer for epitaxial growth of a light emitting structure laminate, which also serves as a lift-off layer for separating the light emitting structure laminate from a sapphire substrate.